Investors should not worry—the stock market is not rigged by high-frequency trading, Tom Joyce, former chief executive officer of Knight Capital, told CNBC's "Closing Bell" Tuesday.
"The retail investor should have no concerns at all about high-frequency trading," he said.
"High-frequency traders, assuming they're not doing anything nefarious like front-running or getting favored treatment…just have a different time horizon than anybody else."
Critics of high-frequency trading include noted author Michael Lewis, who made the claim in his book "Flash Boys" that the market is rigged by high-frequency traders who front-run orders.
Calling Lewis "dead wrong" and the term rigged "irresponsible," Joyce said, "I can't get too twisted about some people who get their PhDs in applied mathematics or physics and instead of pursing a job at Boeing or Google, they decide to apply their skills to the stock market."